This application claims priority of Japanese Patent Application No.2000-349702 filed in JPO together on Nov. 16, 2000, the entire disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an image forming machine of cleaner-less type for improving the quality of an image forming to a recording medium by removing effectively a toner accumulated in a memory removing brush.
2. Description of the Related Art
According to the image forming machine of electro-photographic type, a cleaning processing for removing untransferred toner remaining on the surface of a photoconductive drum is necessary. For the cleaning processing, the image forming machine comprises a cleaner including a blade for scraping off the untransferred toner from the surface of the photoconductive drum.
When providing such cleaner in the image forming machine, there is a problem in that a maintenance for members such as a blade becomes necessary. Therefore, an image forming machine of cleaner-less type for reusing the untransferred toner remaining on the surface of the photoconductive drum after collecting with the developer, is developed. The image forming machine of cleaner-less type has an advantage in that the structure is simplified since a cleaner is not provided.
In the image forming machine of cleaner-less type, to scatter the untransferred toner remaining on the surface of the photoconductive drum, a memory removing member (such as a brush) is provided. When the toner adheres to the memory removing brush and accumulates, the memory removing effect decreases. Therefore, during the operation sequence of the image forming machine, a cleaning sequence for the memory removing member is inserted.
When the toner is accumulated in the memory removing member, the resistance value of the memory removing member increases, and the current flowing into the memory removing member decreases. A special attention was paid to the electric characteristic of such memory removing member, and an image forming machine which detects the current flowing into the memory removing member, judges that an excess toner has accumulated in the memory removing member when the detected current becomes less than the predetermined value, and then carries out a cleaning sequence to the memory removing member, is proposed.
The cleaning sequence for the memory removing member proposed conventionally sets the timing to start the cleaning when the absolute value of the detected value of the current flowing into the memory removing member becomes lower than the predetermined value, and the cleaning time was fixed. Therefore, when the toner of amount beyond expectation is accumulated in the memory removing member, there were cases in which the toner cannot be removed fully during a fixed period of time. As a result, there were problems in that the quality of the image forming to the recording medium decreases due to the generation of white areas in the image by the photoconductive body failing to be charged.
The present invention was made in consideration to such situation, and it is thus the object of the present invention to provide an image forming machine of cleaner-less type for removing the toner accumulating in the memory removing brush effectively and improving the quality of the image forming to the recording medium.
According to the first aspect of the present invention, the image forming machine comprises a photoconductive body, a charging member for charging the photoconductive body, a means for forming an electrostatic latent image on the surface of the charged photoconductive body, a developing unit for developing the electrostatic latent image on the surface of the photoconductive body, a transferring unit for transferring a toner image on the photoconductive body to a recording medium, a memory removing member for removing the toner image remaining on the photoconductive body, and a detecting means for detecting the current flowing through the memory removing member, wherein a cleaning sequence of the toner adhered to the memory removing member is carried out, and the length of the time for carrying out the cleaning sequence is changed according to the current flowing through the memory removing member.
Moreover, according to the second aspect of the present invention, the image forming machine comprises a photoconductive body, a charging member for charging the photoconductive body, a mean for forming an electrostatic latent image on the surface of the charged photoconductive body, a developing member for developing the electrostatic latent image on the surface of the photoconductive body, a transferring member for transferring a toner image on the photoconductive body to a recording medium, a memory removing member for removing the toner image remaining on the photoconductive body, and a detecting means for detecting the current flowing through the memory removing member, wherein a cleaning sequence of the toner adhered to the memory removing member is carried out, and the frequency for carrying out the cleaning sequence is changed according to the current flowing through the memory removing member.
Furthermore, according to the third aspect of the present invention according to claim 2 of the present invention, the image forming machine is characterized in that the cleaning sequence is carried out each time the image is formed on the recording medium of a predetermined quantity, and the frequency to carry out the cleaning sequence is changed by changing the quantity of recording medium on which the image is formed.
According to the first aspect, the length of the time to carry out the cleaning sequence is changed according to the current flowing through the memory removing member. Therefore, when the absolute value of the detected value of the current flowing through the memory removing member is small due to the increased amount of the toner accumulated in the memory removing member, by lengthening the time to carry out the cleaning sequence, the toner accumulated in the memory removing member can be removed effectively. As a result, the quality of the image forming to the recording medium can be improved.
According to the second aspect, the frequency for carrying out the cleaning sequence is changed according to the current flowing through the memory removing member. Therefore, when the absolute value of the detected value of the current flowing through the memory removing member is small due to the increased amount of toner accumulated in the memory removing member, by increasing the frequency to carry out the cleaning sequence, in other words, by increasing the number of times for carrying out cleaning sequence within a fixed period of time, the toner accumulated in the memory removing member can be removed effectively. As a result, the quality of image forming to the recording medium can be improved.
According to the third aspect, the frequency for carrying out the cleaning sequence is changed by changing the quantity of the recording medium of which the image is formed. Therefore, since the cleaning sequence is carried out after the image is formed on the recording medium within a limited quantity, and since the generation of time wherein the image cannot be formed on the recording medium by unnecessary cleaning sequence is prevented, the image forming to the recording medium can be carried out efficiently.